Directional control valve

ABSTRACT

A four-way spool valve assembly embodying a regenerative circuit for controlling the actuation of a double acting fluid motor for a bulldozer blade or the like characterized in that the spool has therewithin a relief valve and a check valve respectively operative to build up back pressure in the return line from the rod end of the motor during the blade lowering operation and to permit return flow under such back pressure into the inlet port to prevent cavitation of the head end of the motor, and further characterized in that the spool has a float position in which a bypass passage in the assembly is open for flow of fluid from the inlet passage to the return passage and in which both motor ports have unrestricted communication with the return passage.

United States Patent 1 1 Paul [ DIRECTIONAL CONTROL VALVE John C. Paul,West Richmond Heights, Ohio [75] Inventor:

[73] Assignee: Parker-Hannifin Corporation,

Cleveland, Ohio 1221 Filed: Apr. 19, 1972 21 Appl. No.2 245,451

1 1 July 17, 1973 Primary Examiner-Henry T. Klinksiek Attorney-WalterMaky [57] ABSTRACT A four-way spool valve assembly embodying aregenerative circuit for controlling the actuation of a double actingfluid motor for a bulldozer blade or the like characterized in that thespool has therewithin a relief valve and a check valve respectivelyoperative to build up back pressure in the return line from the rod endof the motor during the blade lowering operation and to permit returnflow under ,such back pressure into the inlet port to prevent cavitationof the head end of the motor, and further characterized in that thespool has a float position in which a bypass passage in the assembly isopen for flow of fluid from the inlet passage to the return passage andin which both motor ports have unrestricted communication with thereturn passage.

6 Claims, 1 Drawing Figure RAISE Pmmzumlmn TANK FLOAT NEUTRAL---- RAISEDIRECTIONAL CONTROL VALVE BACKGROUND OF THE INVENTION It is known toprovide regenerative circuits as abovementioned in connection with frontend loaders, for example to prevent fluid motor cavitation as during theload (boom and bucket) lowering operation thereof when the load on themotor tends to run ahead of the pump. See, for example, the applicationof Rice Ser. No. 1715, filed Jan. 9, 1970, now U. S. Pat. No. 3,642,027wherein the spool is hollow and has therein a relief valve and a checkvalve respectively operative to build up back pressure in the returnline from the motor during the load lowering operation and to permitreturn flow under such back pressure into the inlet port to preventcavitation of the fluid motor.

It is also known to provide a four-way spool type valve assembly inwhich the spool has a float position to permit movement of the piston ofa fluid motor in a direction such that oil coming out of the head end ofthe cylinder is conducted to the rod end of the cylinder via a passagein the spool with excess flow passing through a spring loaded valve oran orifice leading to the low pressure side of the valve assembly. Forexamples of this type of four-way float spool, reference may be had tothe following U.S. Pats.:

Schmiel, No. 3,000,397; Stacey, No. 3,195,559; Stacey, No. 3,106,065;Stacey, No. 3,251,277; Markovich, No. 3,120,858; Stacey, No. 3,262,467;Stacey, No. 3,132,668; Stacey, No. 3,299,903; and Schmiel et 7 al., No.3,160,174.

In the case of equipment such as a front end loader the downward floatof the boom and bucket displaces oil from the head end of the cylinderto the rod end with excess flow being conducted to the low pressure sideof the valve assembly. However, in the case of a bulldozer or the like,the bulldozer blade may be employed for back dragging while the valveassembly is in the float position and hence oil is discharged from therod end of the cylinder to the head end. Accordingly, such orificecommunication of the motor ports with the low pressure side of the valveassembly as described in the aforementioned patents cannot be usedbecause oil would have to be drawn into the head end of the cylinderthrough such restricted orifice thereby causing cavitation in the headend of the motor. In such bulldozer application it is of coursenecessary when the blade is in operating position to press it firmlyagainst the ground and hence oil under pressure is admitted into thehead end of the cylinder for maximum ground engaging force, whereas in afront end loader or the like,

oil is admitted into the head end of the cylinder to raise the boom andbucket.

SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWING to theactuating cylinder for a bulldozer blade or the like.

DETAILED DESCRIPTION OF THE INVENTION.

The directional control valve assembly 1 herein shown comprises ahousing 2 having a pressure inlet port 3 adapted for connection with apump 4, a return port 5 adapted for connection with a tank 6, and a pairof motor ports 7;7 adapted for connection with a double acting fluidmotor 8.

The housing 2 is of conventional form having a bore 9 therethrough for aspool 10, said bore 9 being intersected axially therealong starting fromthe middle by a bypass passage portion 11 which leads to the return port5, said bypass portion 11 being straddled by bypass portions 12;l2leading to the inlet port 3, a pairof pressure feed passages 14,14 whichstraddle the aforesaid bypass portions I2;l2 and of which the lowerpassage 14 communicates with the inlet port 3 via load check valve 15, apair of motor passages, l6;l6 which straddle the pressure feed passagesI4;14 and which lead to the respective motor ports 7;7, and a pair ofreturn passages 17;17 which straddle the motor passages l6;l6 and whichlead to the return port 5. Between the inlet port 3 and one returnpassage 17 is the main relief valve 13.

When the spool 10 is in NEUTRAL position in which it is held by thespring centering mechanism 18, fluid delivered by the pump 4 to theinlet port 3 freely circulates through the bypass passages l2;l2 and 11back to the tank 6 through the return port 5, and the motor passagesl6;16 are blocked from communicating with the return passages 17;l7 bythe lands l9;l9, and are blocked from communicating with the lower feedpassage 14 and with the upper inlet branch 12 by the respective spoollands 20;20, whereby the bulldozer blade 21 and boom 22 will remain inwhatever position they happen to be when the spool 10 is allowed to beshifted by the spring centering mechanism 18 to NEU- TRAL position.

In one end of the spool 10 is a relief valve member 23 which is actuatedto seated position by the spring 24 and which is operative to maintain apredetermined back pressure in the regeneration path hereinafter to bedescribed when the spool 10 is in LOWER position, said relief valvemember 23, when actuated by pressure exceeding the predetermined backpressure, opening a first passage constituted by the openings 25, thebore 26, and the holes 27 which then register with the upper returnpassage 17, to relieve excess pressure to the return passage 17.

The upper load check valve 15 is disposed between the upper feed passage14 and the upper motor passage 16 and hence when the spool 10 is shiftedto RAISE position fluid under pressure will be conducted to the uppermotor passage via the openings 28 in upper land 20, bore 29, openings25, upper feed passage 14, and upper load check valve 15.

In the other end of the spool 10 is a check valvemember 30 which isurged to seated position by the spring 31 and which is operative whenthe spool 10 is in LOWER position to open a second passage in theregeneration path which is constituted by the openings 25, the bore 29,and the openings 32 for flow of fluid into the lower bypass passageportion 12 to supplement the fluid delivered by the pump 4 thus toprevent cavitation when the spool is in its power LOWER" position. Thisprovides for fast lowering of the blade 21 to ground engaging position.

When it is desired to lower the boom 22 with the blade 21 firmlyengaging the ground as aforesaid, the spool 10 is shifted upwardly fromNEUTRAL position to LOWER position, whereat the spool lands 34 and 20close communication between the bypass por- -tions 12 and 11 for flow offluid under pressure delivered by the pump through the lower check valveto the lower pressure feed passage 14 and thence to the lower motorpassage 16 via the spool groove 35 whereby fluid under pressure isconducted into the head end of the motor 8 to move the boom 22 and blade21 downwardly. Oil displaced from the rod end of the motor 8 flows intothe upper motor passage 16 and because of the closed position of therelief valve member 23 pressure builds up in the upper motor passage 16and effects unseating of the check valve member 30, whereby the fluidreturning to the valve assembly 1 from the rod end of the motor 8 isconducted into the inlet port 3 to supplement the pump 4 output, thus toachieve rapid lowering of the boom under power control and withoutpermitting cavitating of the head end of the motor 8. I

As the blade 21 contacts the ground, pressure starts to build up in theinlet port 3 sufficient to close the check valve member 30 and theincreased pressure in theupper motor passage 16 acting on the area ofthe relief valve member 23 moves the same to open position and whenopened the pressure drop across the annular orifice 36 acting on thelarger diameter of the relief valve member 23 opens the relief valvemember 23 further and maintains it open for prompt reduction of pressurein the return circuit to a value less than initially required to unseatthe relief valve member 23. Thus, the increased pressure acts on thehead end of the motor 8 to firmly press the blade 21 into the ground.

When it is desired to raise the boom 22 and blade 21, the spool 10 isshifted downwardly from NEUTRAL position to RAISE position whereat thespool lands 34 and block communication between the bypass portions 12and 11 with fluid under pressure in the inlet port 3 being conductedthrough openings 28, bore 29, openings 25, upper feed passage 14, andupper check valve 15 into the upper motor passage 16 for flow into therod end of the motor 8. Fluid displaced from the head end of the motor 8is conducted to the lower motor passage 16 and to the lower returnpassage 17 via the spool groove 35. When the force on the spool 10 isreleased, the spring centering mechanism 18 will return the spool 10from the RAISE position back to "NEUTRAL" position.

When the spool 10 is in FLOAT position, the boom 22 and blade 21 mayfloat up or down, the lower motor passage 16 being communicated with thelower return passage 17 by way of the spool groove 37, and the uppermotor passage 16 being communicated with the upper return passage 17 byway of the spool groove 38. In FLOAT position the bypass passage 12-11is open as shown.

I, therefore, particularly point out and distinctly claim as myinvention:

1. In a spool valve assembly having a housing including a pressure inletport, a return port, and a pair of motor ports; a valve spool movable insaid housing to control actuation of a double acting fluid motor adaptedto be connected to said motor ports and having first and second groovesrespectively communicating one motor port selectively with said inletport and said return port and the other motor port with said inlet portwhen said one motor port is communicated with said return port via saidfirst groove; said valve spool, in addition to said grooves, havingfirst and second passages therein respectively communicating said othermotor port with said return port and with said inlet port when said onemotor port is communicated with said inlet port; a relief valve in saidfirst passage to build up back pressure in returning fluid in said othermotor port; and a check valve in said second passage permittingreturning fluid flow into said inlet port in the event of decrease offluid pressure in said inlet port to a value less than the back pressurein said other motor port when said spool is in a position communicatingsaid inlet port with said one motor port; the improvement whichcomprises a valve spool in which said first and second passages,upstream of said relief valve and check. valve, both open in said secondgroove and in a land adjacent to said second groove to respectivelycommunicate with a passage in said housing leading to said other motorport and with said inlet port when said spool is in a positioncommunicating said one motor port with said return port.

2. The valve assembly of claim 1 wherein said housing passage hasanother check valve therein to prevent reverse flow of fluidtherethrough.

3. The valve assembly of claim 1 wherein said valve spool has a floatposition whereat both motor ports are communicated with said return portvia said second groove and via a third groove in said spool "adjacent tosaid first groove.

4. The valve assemblyof claim 3 wherein said first and second passages,downstream of said relief and said check valve, terminate in openingsthrough other spool lands adjacent to said second groove and said firstgroove to communicate respectively with said return port and inlet portwhen said spool is in a position communicating said inlet port with saidone motor port.

5. In a spool valve assembly having a hosuing including a pressure inletport, a return port, and a pair of motor ports; and a valve spoolmovable in said housing to two operating positions to control actuationof a double acting fluid motor adapted to be connected to said motorports and having first and second grooves selectively communicating saidmotor ports with said inlet and return ports; the improvement whichcomprises a valve spool having a third groove adjacent to said firstgroove operative in conjunction with said first groove to communicateeach motor port with said return port upon movement of said valve spoolto a third operating position whereby the movable component of the fluidmotor may float in opposite directions; said spool being hollow andhaving openings thereinto through a land adjacent to said second grooveto communicate with said inlet port and through said second groove; andsaid housing having a passage communieating said second groove with saidother motor port when said spool is in a position communicating said oneposition whereat one motor port is freely communicated with said returnport via said second groove and the other motor port is freelycommunicated with said return port via a third groove in said spoolwhich is adjacent to said first groove thus to permit free floating ofthe movable component of the fluid motor in opposite directions; saidspool having a passage therein which opens to said inlet port and tosaid second groove when said spool is in a position communicating saidother motor port with said return port via said first groove; saidhousing having a passage communicating with said second groove and saidone motor port when said spool is in the last-mentioned position.

1. In a spool valve assembly having a housing including a pressure inletport, a return port, and a pair of motor ports; a valve spool movable insaid housing to control actuation of a double acting fluid motor adaptedto be connected to said motor ports and having first and second groovesrespectively communicating one motor port selectively with said inletport and said return port and the other motor port with said inlet portwhen said one motor port is communicated with said return port via saidfirst groove; said valve spool, in addition to said grooves, havingfirst and second passages therein respectively communicating said othermotor port with said return port and with Said inlet port when said onemotor port is communicated with said inlet port; a relief valve in saidfirst passage to build up back pressure in returning fluid in said othermotor port; and a check valve in said second passage permittingreturning fluid flow into said inlet port in the event of decrease offluid pressure in said inlet port to a value less than the back pressurein said other motor port when said spool is in a position communicatingsaid inlet port with said one motor port; the improvement whichcomprises a valve spool in which said first and second passages,upstream of said relief valve and check valve, both open in said secondgroove and in a land adjacent to said second groove to respectivelycommunicate with a passage in said housing leading to said other motorport and with said inlet port when said spool is in a positioncommunicating said one motor port with said return port.
 2. The valveassembly of claim 1 wherein said housing passage has another check valvetherein to prevent reverse flow of fluid therethrough.
 3. The valveassembly of claim 1 wherein said valve spool has a float positionwhereat both motor ports are communicated with said return port via saidsecond groove and via a third groove in said spool adjacent to saidfirst groove.
 4. The valve assembly of claim 3 wherein said first andsecond passages, downstream of said relief and said check valve,terminate in openings through other spool lands adjacent to said secondgroove and said first groove to communicate respectively with saidreturn port and inlet port when said spool is in a positioncommunicating said inlet port with said one motor port.
 5. In a spoolvalve assembly having a hosuing including a pressure inlet port, areturn port, and a pair of motor ports; and a valve spool movable insaid housing to two operating positions to control actuation of a doubleacting fluid motor adapted to be connected to said motor ports andhaving first and second grooves selectively communicating said motorports with said inlet and return ports; the improvement which comprisesa valve spool having a third groove adjacent to said first grooveoperative in conjunction with said first groove to communicate eachmotor port with said return port upon movement of said valve spool to athird operating position whereby the movable component of the fluidmotor may float in opposite directions; said spool being hollow andhaving openings thereinto through a land adjacent to said second grooveto communicate with said inlet port and through said second groove; andsaid housing having a passage communicating said second groove with saidother motor port when said spool is in a position communicating said onemotor port with said return port via said first groove.
 6. In a spoolvalve assembly having a housing including a pressure inlet port, areturn port, and a pair of motor ports; and a valve spool movable insaid housing to control actuation of a double acting fluid motor adaptedto be connected to said motor ports and having two operating positionswhereat first and second grooves therein selectively communicate saidmotor ports with said inlet and return ports; the improvement whichcomprises a valve spool having a third operating position whereat onemotor port is freely communicated with said return port via said secondgroove and the other motor port is freely communicated with said returnport via a third groove in said spool which is adjacent to said firstgroove thus to permit free floating of the movable component of thefluid motor in opposite directions; said spool having a passage thereinwhich opens to said inlet port and to said second groove when said spoolis in a position communicating said other motor port with said returnport via said first groove; said housing having a passage communicatingwith said second groove and said one motor port when said spool is inthe last-mentioned position.